This invention generally relates to electrical connections capable of mechanical movement, and more particularly to an improved cardiac pacer lead incorporating an electromechanical connection for providing an electrical connection between a rotatable terminal pin and an external pacer terminal casing.
A conventional cardiac pacer lead includes an electrode at its distal end and a cardiac pacer or pulse generator terminal at its proximal end. The two ends are interconnected by an insulating sleeve or sheath that is inert to body fluids and that contains an electrical conductor therewithin. The distal end electrode, which may be porous, must be properly manipulated so that it is brought into contact with the cardiac tissue that it will subsequently activate. The surgeon implanting the pacer lead typically inserts the pacer lead into the patient by way of a surgical incision in the chest cavity and through appropriate body passageways for attachment of the electrode to cardiac tissue in an atrial or ventricular heart chamber. These insertion techniques are greatly facilitated by structuring the lead to permit rotation of the electrode within the insulating sleeve which is connected to the terminal end to allow the surgeon to properly position the electrode end by manipulating the terminal end which is exterior of the body so that the surgeon is certain that the electrode end of the pacer lead makes contact at the desired cardiac tissue location.
It therefore becomes desirable to equip cardiac pacer leads with a terminal end that, when rotated, will rotate the distal electrode. Due to this needed rotatability, it further becomes desirable to supply a pacer lead terminal pin with a reliable electrical connection that allows substantially unrestricted rotation of the terminal end and transmits current from the pacer through the terminal to the electrode.
One generally known method of obtaining such an electromechanical connection involves the use of "spring fingers" at the pacer lead proximal end, that is, a series of slender electrically conductive strips extending longitudinally from the pacer lead, each strip having a radially inwardly extending catch at its forwardmost end that engages an annular rib on the terminal pin shaft. This type of connection, although adequate and reliable, presents potential problems in that excessive pressure upon the spring fingers by the surgical team while handling or inserting the pacer lead can potentially deflect the spring fingers outwardly so that one or more of the spring fingers disengage the terminal end. Additionally, with this type of connection the terminal pin is not entirely contained within the pacer lead assembly. When this connection is flexed excessively, the spring fingers have a tendency to slightly separate from the terminal pin. It therefore becomes desirable to supply an improved electromechanical connection encased within a pacer lead terminal end that will allow unrestricted rotation of the pacer terminal pin within the terminal casing while providing a plurality of pressure contact points between the outer casing and the terminal pin.
The present invention provides this type of enhanced reliability in an electrical connection by providing a flexible and conductive coil that is deformed to provide a generally continuous but non-uniform helical shape in which individual turns of the coil adjacent one another randomly extend radially outwardly from the coil axis. In an important aspect of this invention, the coil is inserted over the terminal pin shaft of a pacer lead and retained on the terminal pin by an external casing that allows rotation of the terminal pin therein. Outward radial protrusions of the coil provide multiple contact points having proper contact pressure to electrically connect the terminal casing to the pacer terminal pin while allowing unrestricted rotation of the terminal pin within the casing. The coil has an inner diameter, as defined by the inwardlymost positioned turns, that is less than that of the terminal pin, and these inwardlymost positioned turns engage and continuously contact the pin.
It is accordingly a general object of the present invention to provide an improved multi-contact electromechanical connection.
Another object of this invention is to provide an improved electromechanical connection for use within a cardiac pacer lead wherein the proximal end terminal pin is capable of unrestricted rotating movement.
A further object of this invention is to provide an improved pacer lead having an electromechanical connection entirely contained within the pacer proximal end casing that allows rotation of the cardiac terminal pin.
Another object of the present invention is to provide a compact electromechanical connecting assembly that is especially suitable for a pacing lead having bipolar electrodes.
A still further object of this invention is to provide a multi-contact electomechanical connection incorporating a springwire coil having a non-uniformly deformed generally helical shape such that individual coil turns adjacent one another are generally radially spaced from one another to create a plurality of internal and external electrical contact points.
Another object of the present invention is to provide a compact electromechanical connection that has a minimal longitudinal extent.